Today it is very energy demanding to produce hydrogen, when the whole energy accounts are estimated from raw material too compressed or liquefied hydrogen. With today's technology the hydrogen will be 20-30% more expensive than alternative fuel like gasoline, diesel etc. with the same energy content.
At the same time the most effective production units is large, complicated and expensive. They also demand frequent maintenance routines which is part of making produced hydrogen more expensive.
Today most of the hydrogen production is accomplished by steam reforming where the residue CO2 gets out in to the atmosphere, which is climatic destroying. It is being researched on handling this problem and with known technology it will demand 20-30% equivalent the energy in hydrogen to depositing CO2 in for example hydrocarbon reservoirs, where it can be extracted more hydrocarbons at the same time.
When heat is needed during the hydrogen production, it is researched on being able to recycle the thermal energy, which they have managed at MIT with totally 95%.
In an earlier Norwegian patent application 20064407 it is described a device and method for hydrogen production by electrolysis. The device contains a compact rotating hydrogen production unit which can deliver separated gas pressurized out of the device helped by regulating valves at the outlet of the device. However the regulating valves and the slip chambers established at the ends of the shafts could be exposed to quick wear, leaking and resistance.